<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>


</head>
<body>
   
        <button onclick="start()">点我</button>
        
        <button onclick="stop()">停止</button>

    
</body>
<script>
    var myvar;
    function start(){
       myvar= setTimeout(function(){
            alert("您好")
        },3000)
    }

    function stop(){
        clearTimeout(myvar)
    }


</script>
</html>